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FloodMapp NowCast for live traffic routing

Helping City of Norfolk, VA to adapt to climate change

The City of Norfolk, Virginia (USA) has 144 miles of shoreline along lakes and rivers as well as Chesapeake Bay. Norfolk is home to some 247,000 residents. Much of this land is located in residential neighborhoods. This City is home to a diverse and thriving economy and the world’s largest naval base, and the North American Headquarters for NATO (North Atlantic Treaty Organization).

Flooding has been part of most people’s lives there for the last century, however in more recent years, flooding has become more problematic and a risk to public safety.

There are three main types of flooding that occur in Norfolk. The most frequent is often referred to as “sunny day flooding”, where north-easterly winds and land subsidence combine to create coastal flooding on days that have clear skies. Secondly, sea level rise from climate change has led to high tides getting higher, causing the city’s stormwater network to lose its efficiency and cause flooding. And finally, flash flooding (pluvial) from thunderstorms, which though short in duration, produce high-intensity rainfall leading to flooding.

A major problem experienced throughout the city is the increased frequency of flooded roads causing significant disruptions to transport which impacts economic and social activity. For example, by preventing drivers and other commuters from accessing their usual day-to-day routes, including getting home or collecting children from school. While (thankfully) in most cases, this is non-life-threatening flooding, it does cause significant disruption to transport networks as well as the loss or damage of many cars and vehicles. Further, as floodwater is mostly saltwater in Norfolk, there is a high risk of corrosion to cars caught in flood waters affecting car braking systems and other metal components which can be costly to repair.

While less frequent, high-velocity pluvial flooding can occur in Norfolk, creating hazards in areas with steeper slopes, and the potential for severe and life-threatening risks.

The City had access to a lot of information including flood sensors, and static flood studies. But given the speed and scale of unfolding flood events, little actionable intelligence was available.  Any solution to this problem had to be timely, accurate, and targeted.  The City sought help from RISE; who put out a global call with their Urban Mobility Resilience Challenge, seeking real-time flood modelling technology which could be used to help traffic navigate around flooded roads.

RISE is a non-profit, economic development organization with a mission to accelerate innovation and business growth around solutions to coastal communities’ resilience challenges. RISE enables businesses to develop, demonstrate and scale innovations that help coastal communities adapt to changing climate.

FloodMapp, through RISE Resilience Innovations' Urban Mobility Resilience Challenge, was selected in 2020 to leverage our unique technology and products to deliver real-time, street-level intelligence of flooded roads in the City of Norfolk to assist City officials with situational awareness, and to predict and alert citizens to flood hazards and road closures. 

This project was made possible by a grant from RISE, which is funded through Community Development Block Grants from the U.S. Department of Housing and Urban Development and administered through the Virginia Department of Housing and Community Development.

The aim was to integrate FloodMapp with Norfolk’s existing ESRI ArcGIS products. The desired outcome was to help the City of Norfolk mitigate risk by providing real-time flood intelligence for emergency operations, while concurrently providing flooded road conditions directly to drivers via the Waze for Cities program.


FloodMapp worked with the City of Norfolk to understand the detailed use case requirements to solve this challenge.  Leveraging the power of NowCast’s real-time capability, FloodMapp was able to identify and access the data needed to meet the speed, accuracy, and granularity required to genuinely solve this challenge. NowCast was implemented to run and refresh results every 15 minutes as new tidal and rainfall observations are ingested, producing 1m resolution flood inundation models, accurate within inches.

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Figure 2: NowCast generates real-time street-level intelligence on flood inundation extent and depth.

City road data was used in RoadSafe, a powerful analytics service which predicts flooded roads based on NowCast inundation data. Flood depth thresholds, developed in collaboration with the City, are used to define road hazards and road closures respectively based on the depth of flooding over each road segment.

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Figure 3: (above) Dynamic gif of FloodMapp NowCast and RoadSafe which shows predicted road hazards (yellow) and closures (red) impacted by tidal flooding in Norfolk as the water level rises and falls.

The solution was then delivered to Norfolk’s ArcGIS Online organization, where they can view live road closures and road hazard segments which update dynamically as a flood unfolds.

Figure 4: Esri ArcGIS Online dashboard showing live road hazard and closure data.

 In many ways, Norfolk provided an optimal challenge to test FloodMapp. FloodMapp’s core technology is designed to function at scale so projecting the model over a citywide area was a good fit, and regular flooding in the area helped improve the models on a more consistent basis. That said, as a focus of the project was to account for flooding on roads, and with Norfolk having thousands of roads, the team had to focus on additional details such as the characteristics of roads and bridges and validate content within this urban landscape.

Accounting for discrepancies in forecasts also provided FloodMapp with learning opportunities. Each rainfall event is different and, as most people know, accurately forecasting weather is a tricky science. At FloodMapp we often talk about being one link in the chainmail of defence for situational intelligence and certainly having accurate forecasts helps boost the efficacy of FloodMapp.

In partnership with RISE and the City of Norfolk, we had a team of drivers who were able to help us validate the models against ground observations.

Figure 5: FloodMapp team undertaking validation of NowCast models near Mowbray Arch, Norfolk, VA

Figure 6: Measured water depth, ~9 inches, on Richmond Crescent, corresponding simulated depth at same approximate time and similar location was ~10 inches (yellow indicates depth measurement location)

Validation showed that not only was NowCast highly accurate in predicting flood extent, it was also capable of accurately predicting flood depth to within an inch.


The next part of the challenge required working with another Esri partner, Waze. In a world-first, FloodMapp simultaneously integrated RoadSafe flooded road predictions with the Waze app via the Waze for Cities platform.  This data is then sent to drivers as a flood hazard icon in their Waze app, which quickly alerts them to flood hazards in real-time and enables safe route planning to navigate away from delay or danger.

Waze’s road closure algorithms work to safely re-route motorists around high hazard flood waters.

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Figure 7: Road closures on Hampton Boulevard, Norfolk – FloodMapp NowCast (left), corresponding FloodMapp RoadSafe road closures in Waze (right)

Furthermore, motorists can contribute feedback via the Waze, through the 'Thumbs up’ or flood hazard reporting feature. This powerful crowdsourced ground-truth data enables real time monitoring of model performance. The data is valuable for ongoing validation, allowing FloodMapp to continually improve flood model performance and road closure predictions going forward. This ensures the highest level of ongoing quality assurance as the models can dynamically adapt to changes in the City environment. Perhaps due to Norfolk being a city so often flooded, we had a willing cohort of citizen scientists who helped with ground-based observations, like photographs and videos, to help us validate the models at a street-level.

Another challenge was in testing the pluvial (flash flooding) model over a large area. There are many modelling complexities involved with pluvial flooding that had to be simplified to achieve the desired outcomes of the challenge, real-time intelligence and modelling.


FloodMapp NowCast and RoadSafe flood intelligence are delivered and rendered as a City-wide common operating picture and single point of truth via Esri’s ArcGIS Online and ArcGIS Pro systems. This provides the City of Norfolk staff and Emergency Operations Centre (EOC) with hyper-local flood intelligence in real-time.  This vital situational awareness has helped to inform emergency managers and public works officials in their operational response to flooding, which supports in delivering community messaging, planning, and response decision-making. 

Image 8: FloodMapp RoadSafe generates flood hazard notifications in Waze to alert drivers and also invite them to verify the accuracy of flood hazards by giving a thumbs up

This technology is helping the City to adapt to climate change and ultimately build a more resilient community. 

“As our streets flood more often due to climate change, we need to find a sustainable way to alert community members about the risks they face. FloodMapp’s technology provides affordable, citywide situational awareness that current solutions, such as sensor networks alone, don’t offer.” - Kyle Spencer, Deputy Resilience Officer for the City of Norfolk.

Figure 9 - Heatmap showing the clustering of all the FloodMapp/City of Norfolk confirmed flooded roads since we went live with Waze on Oct 2021

Concurrently, citizens can access FloodMapp RoadSafe via their Waze App, which quickly alerts them to flood hazards in real-time and enables safe route planning to navigate away from delay or danger.

Since launching the system live to residents in October 2021, Waze users confirmed more than 4,348 flooded roads predicted by FloodMapp RoadSafe. Drivers have provided over 9,452 thumbs-ups to validate these predictions (an average of 2.2 and a maximum of 72 confirmations per hazard). Not only do these serve as crowdsourced observations to aid in validation and ongoing model improvement; the engagement statistics indicate the impact that the app is having to help thousands of drivers navigate around flooded roads. Those drivers have now prevented loss or damage to their vehicles and have been able to get home safely to their families.

“The successful integration of FloodMapp’s technology into Waze has the potential to save property and lives and help coastal communities worldwide adapt to the threats from climate change,” - Paul Robinson, RISE Executive Director

The FloodMapp RoadSafe solution has provided an infusion of much needed innovation for the City of Norfolk in adapting to the effects of flood-based hazards.  The solution is highly responsive to localized resilience issues.  It is also sufficiently robust to rapidly adapt to the needs of other communities.

Importantly, RoadSafe data for both city officials and citizens is a delivered by single, shared and accurate source. This will serve to avoid community confusion and misinformation. 

Combining the innovation of FloodMapp, the power of Esri’s ArcGIS systems such as ArcGIS Online, and the reach of Waze is a partnership delivering truly outstanding results.     

FloodMapp was proud to work with RISE, WAZE and the City of Norfolk to launch a system that not only helped emergency managers, but made a discerning and direct impact on the lives and safety of people affected by flooding.

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